BUG: 11208. Fix vtkOpenGLExtensionManager crash on VS2003.
BUG: 11208. Fix vtkOpenGLExtensionManager crash on VS2003.

ReadOpenGLExtensions() calls this->RenderWindow->Render() on Win32 machines if Render() has not previously been called. This caused a crash, because Render() calls vtkOpenGLRenderWindow::OpenGLInit(), which was in turn calling vtkOpenGLRenderWindow::SetExtensionManager(0) and then creating a new ExtensionsManager.  The crash only seemed to occur on VS2003. See bug report for more details.

sankhesh/VTK,gram526/VTK,SimVascular/VTK,hendradarwin/VTK,keithroe/vtkoptix,arnaudgelas/VTK,jmerkow/VTK,spthaolt/VTK,gram526/VTK,keithroe/vtkoptix,demarle/VTK,hendradarwin/VTK,jmerkow/VTK,biddisco/VTK,candy7393/VTK,biddisco/VTK,daviddoria/PointGraphsPhase1,daviddoria/PointGraphsPhase1,collects/VTK,candy7393/VTK,berendkleinhaneveld/VTK,keithroe/vtkoptix,candy7393/VTK,keithroe/vtkoptix,hendradarwin/VTK,demarle/VTK,spthaolt/VTK,mspark93/VTK,candy7393/VTK,hendradarwin/VTK,sumedhasingla/VTK,johnkit/vtk-dev,arnaudgelas/VTK,msmolens/VTK,hendradarwin/VTK,ashray/VTK-EVM,jmerkow/VTK,aashish24/VTK-old,keithroe/vtkoptix,arnaudgelas/VTK,berendkleinhaneveld/VTK,demarle/VTK,SimVascular/VTK,cjh1/VTK,aashish24/VTK-old,msmolens/VTK,spthaolt/VTK,sankhesh/VTK,daviddoria/PointGraphsPhase1,sumedhasingla/VTK,arnaudgelas/VTK,ashray/VTK-EVM,mspark93/VTK,gram526/VTK,sumedhasingla/VTK,keithroe/vtkoptix,gram526/VTK,arnaudgelas/VTK,daviddoria/PointGraphsPhase1,berendkleinhaneveld/VTK,cjh1/VTK,candy7393/VTK,mspark93/VTK,berendkleinhaneveld/VTK,candy7393/VTK,SimVascular/VTK,sankhesh/VTK,sankhesh/VTK,mspark93/VTK,demarle/VTK,biddisco/VTK,mspark93/VTK,biddisco/VTK,ashray/VTK-EVM,SimVascular/VTK,aashish24/VTK-old,msmolens/VTK,mspark93/VTK,berendkleinhaneveld/VTK,sankhesh/VTK,msmolens/VTK,SimVascular/VTK,jmerkow/VTK,collects/VTK,johnkit/vtk-dev,keithroe/vtkoptix,jmerkow/VTK,SimVascular/VTK,hendradarwin/VTK,collects/VTK,biddisco/VTK,sumedhasingla/VTK,berendkleinhaneveld/VTK,msmolens/VTK,aashish24/VTK-old,msmolens/VTK,ashray/VTK-EVM,johnkit/vtk-dev,mspark93/VTK,sankhesh/VTK,spthaolt/VTK,collects/VTK,arnaudgelas/VTK,SimVascular/VTK,ashray/VTK-EVM,cjh1/VTK,jmerkow/VTK,keithroe/vtkoptix,sankhesh/VTK,hendradarwin/VTK,spthaolt/VTK,demarle/VTK,ashray/VTK-EVM,berendkleinhaneveld/VTK,daviddoria/PointGraphsPhase1,demarle/VTK,sumedhasingla/VTK,gram526/VTK,gram526/VTK,cjh1/VTK,sumedhasingla/VTK,jmerkow/VTK,biddisco/VTK,SimVascular/VTK,johnkit/vtk-dev,ashray/VTK-EVM,collects/VTK,gram526/VTK,johnkit/vtk-dev,collects/VTK,jmerkow/VTK,aashish24/VTK-old,msmolens/VTK,johnkit/vtk-dev,msmolens/VTK,gram526/VTK,sankhesh/VTK,cjh1/VTK,aashish24/VTK-old,sumedhasingla/VTK,spthaolt/VTK,demarle/VTK,candy7393/VTK,spthaolt/VTK,demarle/VTK,biddisco/VTK,mspark93/VTK,candy7393/VTK,ashray/VTK-EVM,daviddoria/PointGraphsPhase1,sumedhasingla/VTK,cjh1/VTK,johnkit/vtk-dev